1. Field of the Invention
The invention relates to a deceleration control apparatus for a vehicle. More particularly, an embodiment of the invention relates to a deceleration control apparatus that changes the relation between the mode of operation performed by the driver and a target deceleration, based on whether a vehicle is towing an object.
2. Description of the Related Art
PCT International Publication No. WO00/46063 describes an example of a deceleration control apparatus which includes (a) a target-deceleration setting means that is operated by a driver of a vehicle, and which sets a target deceleration based on a mode of operation performed by the driver, according to a predetermined relation between the mode of operation performed by the driver and the target deceleration; and (b) a deceleration control means for controlling a deceleration of the vehicle by changing a braking force based on the target deceleration set by the target-deceleration setting means. The deceleration control apparatus includes deceleration-request operating members such as a shift lever, a Decel switch, and a Can-Decel switch. The target deceleration is changed continuously or stepwise, in accordance with a change in the mode of operation of the deceleration-request operating member, that is, the number of times that the deceleration-request operating member is operated, or the time period during which the deceleration-request operating member is operated.
However, in a vehicle that can tow a trailer such as a travel trailer, a trailer for carrying a boat, or a trailer for carrying a load, the vehicle weight greatly changes according to whether the vehicle is towing such a trailer. Accordingly, the level of braking performance, that is, a deceleration corresponding to a braking force changes according to whether the vehicle is towing a trailer. As a result, the intended level of deceleration performance may not be achieved. For example, a sufficient level of deceleration performance may not be achieved (i.e., the vehicle may not be sufficiently decelerated). Alternatively, the vehicle may be excessively decelerated. Thus, the driver needs to operate the deceleration-request operating means in different modes to achieve a certain level of deceleration performance, according to the vehicle weight. This impairs the usability of the deceleration control. This problem similarly occurs when the vehicle tows a disabled vehicle or the like.
To prevent such a change in the deceleration performance, a target deceleration (set based on the mode of predetermined operation performed by the driver) may be changed by changing the relation between the mode of operation performed by the driver and the target deceleration, based on whether a vehicle is towing an object. For example, when the vehicle is towing an object, the target deceleration is set to a large value as compared to when the vehicle is not towing an object, even if the driver performs operation in the same mode as when the vehicle is not towing an object. However, for example, if the relation between the mode of operation performed by the driver and the target deceleration is automatically changed, and accordingly the level of deceleration performance corresponding to the mode of operation is changed while the vehicle is running, the driver may feel uncomfortable, and the usability of the deceleration control may be impaired.